The present invention relates to a sputtering apparatus, and a device for exchanging a target and a method for the same. In particular, it relates to a sputtering apparatus suitable for use as an in-line sputtering apparatus for mass production in which a target is frequently exchanged, and to a device for exchanging the target and a method for the same.
A demand for means which may forms various materials into thin films, Such as a sputtering apparatus, has become greater in various kinds of fields. A sputtering method by this sputtering apparatus is such that argon gas or the like is discharged in a vacuum environment of approximately 10.sup.-1 to 10.sup.-4 Torr so as to generate ions for sputtering a target and scattered sputtered particles are accumulated to form a thin film on a surface of a substrate located opposite to the target. Various types of sputtering apparatus employing this principle has been invented and put into practical use.
Particularly, in an in-line sputtering apparatus for mass production, such method is employed that in order to form thin films, each having a predetermined thickness, of plural materials, strength of electric power supplied to targets is regulated to match with each material. According to this method, however, a specific target is often severely consumed so that it must be frequently exchanged. Because a vacuum state of the apparatus is broken every time the target is exchanged, a long period of time for the re-startup of the apparatus is required. Also, a quality of a thin film is unfavorably influenced, which results in a problem that a high quality film cannot always be obtained. Generally, in an in-line sputtering apparatus, such method is employed in such a way that a plurality of targets made of the same kind of material are given for a process while a substrate is being transferred in order to consume the targets as equally as possible. For example, in case of film formation of a magnetic recording disk, a sputtering apparatus continuously forms films on the disk, making use of nearly twenty target electrodes in all for a metallic film, a magnetic film and a protection film. However, when the number of the used targets is increased, an interval of time required for exchanging the targets becomes too long to be neglected and it is the greatest factor to decrease the activity rate of the sputtering apparatus. Particularly, since the film-forming chamber is communicated with the atmosphere during exchanging the targets, a period of re-startup time of the apparatus is not only longer, but preferable films cannot be also obtained as the qualities of the films are unfavorably influenced.
As disclosed in Japanese Patent Unexamined Publication No. 1-165770, such method has already been proposed that a target electrode portion is formed into a unit and the unit is securely attached on a film-forming chamber just by means of a handle or the like, whereby it is made possible to substantially reduce the time for exchanging the target electrode.
Further, as a method for exchanging an adhesion-preventing plate and so on in a film-forming chamber of a sputtering apparatus without communicating with the atmosphere, there is one method as follows.
Disclosed in Japanese Patent Unexamined Publication No. 61-133378 or No. 61-210178 is such method that an adhesion-preventing plate in a film-forming chamber is transferred by an appropriate transfer means to a supply/take-out chamber separated from the film-forming chamber by a gate valve or the like so as to be exchanged in this supply/take-out chamber, and a new adhesion-preventing plate is returned to the film-forming chamber again, whereby the adhesion-preventing plate can be exchanged without communicating the film-forming chamber with the atmosphere. Also, Japanese Patent Unexamined Publication No. 62-20873 or No. 62-127471 discloses such method that in case of exchanging a window glass, the window glass can be exchanged without communicating the film-forming chamber with the atmosphere, by separating a space for exchange of the window glass from the film-forming chamber with a gate valve.
As noted in Japanese Patent Unexamined Publication No. 61-576 which concerns a sputtering apparatus for multilayer film formation, but not an in-line sputtering apparatus, the sputtering apparatus for multilayer film formation is arranged in such a manner that a main chamber is provided with sub-chambers whose number corresponds to that of targets and the main chamber is separated from the sub-chambers by gate valves so that each target is not contaminated during sputtering the other targets.
In the above-described method disclosed in Japanese Patent Unexamined Publication No. 1-165770, the film-forming chamber is communicated with the atmosphere during exchanging the target electrode, which is the greatest factor to decrease a productivity and reliability of the apparatus.
On the other hand, all methods disclosed in Japanese Patent Unexamined Publication Nos. 61-1333378, 61-210178, 62-20873 and 62-127471, are restricted to only exchange of the adhesion-preventing plate and the window glass and cannot be applied to a process of exchanging the target electrode. Further, in a method to utilize a gate valve and an exchanging chamber for the purpose of enabling the target electrode to be exchanged in a vacuum, the gate valve is contaminated by sputtering the target electrode so that the film-forming chamber has to be communicated with the atmosphere to wash the gate valve after all. Moreover, in the method to separate the film-forming chamber from the target electrode by the gate valve in order to form a multilayer film without contaminating each target by the other targets, as explained in Japanese Patent Unexamined Publication No. 61-576, it is possible to exchange the target without communicating the film-forming chamber with the atmosphere, whereas similarly to the above-mentioned other publicly-known instances, it becomes necessary to exchange or wash the gate valve so that the film-forming chamber ,has to be communicated with the atmosphere. In addition, since a structure of the film-forming chamber is complicated and the distance between the target and the substrate is enlarged, such method causes a problem that a film having a favorable property cannot be obtained.
That is to say, in an in-line sputtering apparatus for mass production, a longer period of re-startup time of the apparatus leading to a decrease in an activity rate of the apparatus and an unfavorable influence on the film quality, all of which are resulted from communicating the film-forming chamber with the atmosphere for exchanging thee target, is not fully examined as an important matter to be taken into consideration, in the abovementioned prior arts.